It is the standard practice to support railroad rails by securing them on wooden cross ties with steel tie plates being placed between the cross ties and the rails. The wooden ties, anchored in a bed of crushed stone, provide the proper resiliency for the rails when a heavy load passes over them. Wood ties, however, have short life span, do not abate noise and must be replaced often. Efforts have been made to use concrete and steel cross ties or concrete roadbeds but these attempts have not been too successful because there is no "give" to a concrete or steel block resulting in a hard ride for the rolling stock and a frequent failure of the cross ties and fasteners after a few months under operation.
In known prior art direct fasteners, the fasteners merely cushion the downward forces developed by the rails to a smaller or a larger degree depending on the resiliency and the configuration of the resilient pads placed directly under the base of the rail. All of such known direct fasteners are rigid in relation to the upward motion of the rails that, of course, flex under moving loads of rolling stock. Upward flexing becomes extremely critical under the impact of defective wheels with flats or out-of-rounds. It is believed that failures or damages sustained by presently know direct fasteners used to anchor rails, concrete beds or concrete ties are caused primarily by those extreme conditions produced by defective rolling stock. It is generally recognized that presently available fasteners are too rigid to meet the requirements of modern railroad transportation systems.
In order to obviate the shortcomings of the prior art systems, the present invention is broadly concerned with improved railroad trackage, and is particularly directed towards relieving the anchor pull-out stresses in rigid track bed slabs, as well as the pull-out and twisting stresses developed in the cross ties as induced by the wave action of the rail in moving loads. The subject invention meets the criteria of a fastener that is rigid enough to restrain logitudinal rail movement, while at the same time being resilient enough to accommodate the upward movement of the rail during its wave action when subjected to a moving load. The development of twisting of cross ties induced by out-of-phase wave action of the opposed rails, and by the differential depression and lifting action in the track rails, is prevented by the subject invention by means of the spring plate fastener thereof. With respect to the latter, the subject device utilizes a specially formed steel plate having folded over shoulders which, together with an air entrapped elastomeric molding, forms a rail base and a guideway for the rail. The elastomeric element is of special design and shape, and includes air entrapped pockets which inhibit noise and vibration developed in the trackway.
In the design of the spring plate fastener of the subject invention, the steel spring plate is in combination with an elastomeric rail base supporting element and track bed slabs, beams or cross ties. The subject assembly may be employed in all environments of track installation and geometry, and in all applications dealing with different track alignments. The subject invention greatly improves the track operational properties, and may be employed in conjunction with concrete or steel track beds, as well as in conjunction with wood ties in stone or concrete ballast. The subject device may be employed in new construction, or may be substituted during reconstruction of existing track. Utilizing the subject invention, all of the forces acting on the rail are accommodated; upward forces are dissipated by means of the folded-over shoulders of the steel spring plate; traction or longitudinal forces, as well as lateral or centrifugal forces are transferred into the base of the steel spring plate, thus engaging simultaneously all anchor bolts in shear thereby preventing the latter from bending, breaking or pulling out; and vibrational forces are dissipated by means of the elastomeric rail base supporting element dampening noise and tremors, as more fully described hereinafter.
Utilizing the subject fastening system, easy maintenance as well as improved life of the rail system is achieved. This is especially so when the subject system is employed in subway systems which include sharp curves and are subjected to heavy usage. The subject device is also adaptable for installation of guard or restraining rails parallel to the running or main rail.
Accordingly, it is an object of the subject invention to provide a simple, economical, and highly efficient rail fastener system that can be readily adaptable for a wide variety of usage in either existing or new rail construction. At the same time it is an object of this invention to provide a system that greatly reduces noise polution and vibration transmission to the surroundings.